Polycarbonate refers to polymers formed by combining aromatic or aliphatic dioxycompounds with carbonate ester, and of these, a polycarbonate obtained from 2,2-bis(4-hydroxyphenyl)propane (so-called bisphenol A) is excellent in transparency, heat resistance and mechanical properties such as impact resistance, and it is used in many fields.
In general, polycarbonate is produced from raw materials obtained from petroleum resources, while there are concerns about depletion of petroleum resources, and it is demanded to produce polycarbonate from raw materials obtained from renewable resources such as plants. As biomass materials using renewable resources as raw materials, studies are being made of polycarbonates that use raw materials obtained from ether diol residues producible from glycide in addition to polylactic acid.
For example, an ether diol of the following formula (a) is easily produced from renewable resources such as sugars and starch, and three kinds of stereoisomers are known. Specifically, they are 1,4:3,6-dianhydro-D-sorbitol (to be referred to as “isosorbide” hereinafter in the present specification) represented by the following formula (a-1), 1,4:3,6-dianhydro-D-mannitol (to be referred to as “isomannide” hereinafter in the present specification) represented by the following formula (a-2), and 1,4:3,6-dianhydro-L-iditol (to be referred to as “isoidide” hereinafter in the present specification) represented by the following formula (a-3).

Isosorbide, isomannide and isoidide can be produced from D-glucose, D-mannose and L-idose, respectively. For example, isosorbide can be produced by hydrogenating D-glucose and then dehydrating it with an acid catalyst.
It has been heretofore studied to incorporate in particular isosorbide of the above ether diols into a polycarbonate as the main monomer (Patent Documents 1 to 2 and Non-Patent Documents 1 to 3). However, homopolycarbonates from isosorbide have a very high melt viscosity due to their rigid structures and hence have difficulties in moldability.
For overcoming the above problem, copolymerization with various bishydroxy compounds has been reported. For example, in copolycarbonates of isosorbide with aromatic bisphenols (Patent Document 3 and Non-Patent Documents 4 to 6), aromatic bisphenols themselves have relatively rigid structures and hence work little to decrease the melt viscosity, and these raw materials have a problem that they are derived from petroleum.
Copolycarbonates of isosorbide with alyphatic diols such as 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol and 1,10-decanediol have been reported (Non-Patent Documents 7 to 8). These polycarbonates are block copolymers or random copolymers, and their glass transition temperatures decrease with an increase the length of the aliphatic chains. It has been observed that the glass transition temperatures thereof are 65° C. or 59° C., 26° C. or 20° C., 12° C. or 23° C., or −1° C. or 7° C., and they are poor in heat resistance.
Further, Patent Document 4 describes a molding material comprising a polycarbonate obtained from isosorbide. Although it is said to have a sufficiently high glass transition temperature over room temperature, further improvements thereof in heat resistance are demanded.
On the other hand, Patent Document 5 proposes a polycarbonate that is a copolycarbonate of the ether diol of the above formula (a) with an aliphatic diol and that has a melt viscosity suitable for relatively easy moldability and also has heat resistance. However, the above proposal has a problem that when the polymerization is carried out under reduced pressure at a high temperature, unreacted aliphatic diol is distilled from the reaction system since the aliphatic diol has a low boiling point, so that the compositional ratio of an obtained polymer differs from the charged ratio. When such an aliphatic diol having a low boiling point is used for the copolymerization, the thermal stability is also sometimes insufficient.
Further, Patent Document 6 discusses the copolymerization of a diol having a specific structure and isosorbide, and the glass transition temperature thereof is 100° C. or higher, while further improvements in heat resistance are demanded.
(Patent Document 1) German Patent Laid-open No. 2938464
(Patent Document 2) International Publication No. 2007/013463
(Patent Document 3) JP 56-110723 A
(Patent Document 4) JP 2003-292603 A
(Patent Document 5) International Publication No. 2004/111106
(Patent Document 6) JP 2006-232897 A
(Non-Patent Document 1) “Journal Fuer Praktische Chemie”, 1992, Vol. 334, pp. 298-310
(Non-Patent Document 2) “Macromolecules”, 1996, Vol. 29, pp. 8077-8082
(Non-Patent Document 3) “Journal of Applied Polymer Science”, 2002, Vol. 86, pp. 872-880
(Non-Patent Document 4) “Macromolecular Chemistry and Physics”, 1997, Vol. 198, pp. 2197-2210
(Non-Patent Document 5) “Journal of Polymer Science: Part A”, 1997, Vol. 35, pp. 1611-1619
(Non-Patent Document 6) “Journal of Polymer Science: Part A”, 1999, Vol. 37, pp. 1125-1133
(Non-Patent Document 7) Okada et al, the proceeding of the seventh open symposium on “Polymers with low environmental loads”: Construction of a sustainable material system based on production of plastics with low environmental loads from renewable resources, Scientific Research on Priority Areas (B) supported by Grant-in-Aid for Scientific Research of Ministry of Education, Culture, Sports, Science and Technology, pp. 26-29, 2002
(Non-Patent Document 8) “Journal of Polymer Science: Part A”, 2003, Vol. 41, pp. 2312-2321